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In order to solve the problem of the large moment of inertia of the existing rotating electromagnetic shock absorber for armored vehicles, a new lightweight rotor adaptive electromagnetic shock absorber (LR-AESA) is proposed in this paper. The LR-AESA consists of the left and right symmetrically distributed stators, a rotor in the middle and excitation coils. Secondly, based on the equivalent magnetic circuit method (EMC) and the Ampere loop theorem, and the interaction of the reaction magnetic fields between adjacent eddy current rings and the nonlinear effect of the interaction between the eddy current field and the original magnetic field are further considered, the air gap magnetic field distribution of the LR-AESA of the 10# steel rotor and the copper rotor at different speeds is derived, and the analytical expression of the damping torque is obtained. Finally, the validity of the analytical model was verified by comparison with results from the 3-D finite element method (FEM). The results show that the LR-AESA of the two material rotors can meet the requirements of technical indicators, but in the full speed section (200 ∼ 2000 rpm), the copper rotor has the advantage of a wider range of the damping torque adjustment. [ABSTRACT FROM AUTHOR]

This paper proposes an electromagnetic damping generator (EDG), which is a novel downhole generator for the rotary steerable system (RSS). The EDG is designed to solve the problem of unstable voltage output by the RSS generator. The generator is designed by integrating a traditional generator and an eddy current retarder (ECR). The system converts the excess kinetic energy of the EDG rotor into heating energy by the principle of eddy-current braking and resistance heating. The electromagnetic finite element models of the generator part and ECR part are established and solved by computer. The voltage and torque generated by the generator part and the braking torque of the ECR part are predicted. In the bench test, When the input power is 2537 W < Pinput < 3304 W, the EDG is able to output 300.8 V. When the input power is 3304 W, the output voltage of the ordinary generator is 346 V. The EDG can be adjusted by a decrement of up to 45.2 V to output the rated voltage. The problem of generator output voltage instability in the RSS is solved when mud flow is unstable. [ABSTRACT FROM AUTHOR]

To solve theproblems of an insufficient braking moment for the eddy current retarder at high speed, a small braking moment and slow response of the hydraulic retarder at low speed, and a low power density of the existing electromagnetic hydraulic retarder(EHR), a novel radially distributed electromagnetic-hydraulic retarder(R-EHR) was proposed. The R-EHR fully absorbs the advantages of the braking characteristics of hydraulic retarders and eddy current retarders. The cooling fluid is used to realize the braking of the hydraulic part. At the same time, it acts on the heating surfaces to improve the torque of the electromagnetic part. In this paper, finite element models of the flow field and electromagnetic field are established to predict braking performance. The braking performance of the R-EHR is obtained by bench test, the error between the simulation and experimental data is compared, and the experimental data are analyzed. The results show that the proportion of electromagnetic braking torque in the novel R-EHR is more reasonable. The braking torque increased by 26% and the power density increased by 37.5% at 2000 RPM compared to that of the EHR. The R-EHR can control the braking torque only by adjusting the current, thus simplifying the control system. [ABSTRACT FROM AUTHOR]

In this article, a clear analytical model for predicting the performance of permanent magnet (PM) eddy current couplers is proposed. The interaction of the reaction magnetic fields between adjacent eddy current rings was considered for the first time. Based on a magnetic equivalent circuit (MEC) and the Ampere circuital theorem, the accurate distribution of the air gap magnetic field under different slip velocities was deduced in a 2-D model, and the analytical expression of the transmission torque was obtained. 3-D effects were also taken into account to calibrate the model. The validity of the analytical model was verified by comparison with results from the 3-D finite element method (FEM). The comparison shows that the analytical model can accurately predict the magnetic field distribution and transmission torque over a wide range of slip velocity variations. This model can greatly reduce the number of calculations required and save time, and it is suitable for the preliminary design and optimization of PM eddy current couplers. [ABSTRACT FROM AUTHOR]

To overcome the large power consumption, the braking torque heat recession, and installation difficulties for trailers of eddy current retarder (ECR), a novel self-excited, liquid-cooled, and bridge integrated retarder (SLB-EMR) is proposed in this paper. The structure and work principle of the SLB-EMR are described particularly. Based on the magnetic equivalent circuit (MEC) method, an analytical model of the eddy current braking torque considering magnetic flux leakage and end effect is established. The power generation and braking performance of the SLB-EMR are predicted by the finite element analysis (FEA). We carried out tests for the eddy current braking torque, the heat-fade of braking torque, the no-load loss torque, and natural characteristics of the SLB-EMR respectively. The test results showed that the eddy current braking torque reached 2592 N·m at 1000 r/min. The braking torque declined by 15.5 % after the braking 12 min continuously. The analytical model of eddy current braking torque, and FEA model of the generator and eddy current brake were verified by the test. Compared with the ECR, the SLB-EMR had no-power consumption and low head-fade. [ABSTRACT FROM AUTHOR]

We propose a novel dual air-gaps and liquid-cooled eddy current retarder (ECR) based upon observing the (1) heat fade of the continuous braking and (2) large rotor weight of the traditional ECR for heavy vehicles. The new ECR maintains a low working temperature because of the liquid cooling stator structure. The eddy current distribution and braking torque characteristic curves are obtained by finite element method (FEM). Combining with 3-D FEM, Kriging approximation model is employed to optimize the structural parameters of rotor tooth. Based on the optimization method, the number of rotor teeth is determined to be 12. The braking torque increases by 14.8% after optimization and the rotor tooth weight decreases by 9.5%, which reduces the adverse influence on the vehicle transmission system. The bench test was carried out to verify the optimized calculation results and the braking torque can be stepless controlled by adjusting the excitation current. Compared with traditional ECR, the dual air-gaps and liquid-cooled ECR has better continuous braking performance and is more suitable for heavy vehicle auxiliary braking. [ABSTRACT FROM AUTHOR]

Aiming at the heat fade of the continuous braking and low power density of traditional eddy current retarder (ECR) for heavy vehicles, a new liquid-cooled and flywheel-type eddy current retarder is proposed. The new ECR can keep a low working temperature because of the cooling type. It is assembled between the engine and the clutch, which can effectively improve the braking power density. The transient electromagnetic field of the ECR is solved by the finite-element method, and the braking torque characteristic curve is obtained. The thermal-fluid coupling field is analyzed using the computational fluid dynamics method. Finally, the structure parameters optimization of the rotor tooth is carried out. The braking torque increases by 14.8% and the weight of rotor tooth decreases by 9.5% after optimization. The test results show that the heat fade ratio of the new ECR braking torque is only 8.6%, but that of the traditional ECR is 46.7%. [ABSTRACT FROM AUTHOR]

To both overcome the serious thermal recession problem and conserve energy for conventional eddy-current brakes, a self-excited and liquid-cooled electromagnetic retarder (SL-EMR) assembly is proposed. The design includes a stator with an internally cooled channel, a rotor with multiple magnetic heads, and an integrated generator without brushes. The assembly and operating principles are analyzed. Models of the braking and generating systems are established. The electromagnetic field model analysis, braking performance analysis, thermal field analysis, and generator characteristic analysis of the SL-EMR are simulated using the finite-element method (FEM). The SL-EMR performance is bench tested, and the results show a 6% difference between the FEM results and the experimental results. The integrated generator provides adequate exciting current for the braking system. The braking torque decreases by only 10.4% during continuous braking conditions. The braking torque reached 2000 \N\cdot \m when the speed was 1500 r/min and the coil current was 30 A. [ABSTRACT FROM PUBLISHER]

A transmission tower foundation embedded in frozen soil is subject to both the wind-induced uplift and frost heave forces. The frost heave results in an upward force acting on the foundation, while additional stress induced by the structure load may compress the underlying soils. The freezing- and thawing-induced deformations tend to cause further structural loads and lead to instability problems within the structure. To evaluate the engineering risk and ensure the safety of the Qinghai–Tibet Power Transmission Line (QTPTL) system, stress sensors were installed at the bases of two test tower foundations to investigate the stress state of the tower foundations. Using data on air and ground temperatures, and the deformation of tower foundations, we analyzed the stress variation, and the causes were discussed here. The results showed that the stresses at the bases of tower foundations had a close relationship with air and ground temperatures. The cooling of the underlying soils led to the occurrence of frost heave, which pushed the foundations upward and caused a significant stress bulb under the bases of tower foundations. Seasonal variations in the contact stress depended on the seasonal freezing and thawing of foundation soil. The contact stress increased with the cooling of the underlying soils and decreased with the warming of the underlying soils. The results also showed that the contact stress was free of the wind influence, i.e., the wind-induced uplift force was minor for the contact stress. To fully understand the influences of freezing and thawing on the stress state of tower foundations, a thermal–elasto-plastic finite element model for the tower foundation–soil system was established, and the stresses and deformations of a tower foundation subject to frost heave and thaw settlement were simulated. The results showed that the frost heave force induced by soil freezing potentially threatens the safety and normal operation of the QTPTL. Thaw settlement may lead to harmful deformation of tower foundations if global warming is considered in the numerical model. The remedial measure with thermosyphons only can reduce the settlement of the foundation and will increase the frost jacking risk of the foundation. [ABSTRACT FROM AUTHOR]